- Proton pump
:"This article is about proton pumps in general. For the proton P-type ATPase, see
proton ATPase ."A proton pump is an
integral membrane protein that is capable of movingproton s across the membrane of a cell,mitochondrion , or other subcellular compartment.Function
In
cell respiration , the pumps grab protons from the matrix, the space between the two enclosing membranes of theorganelle , and release the protons within the inner membrane. The confined protons create a difference orgradient in bothpH andelectric charge (ignoring differences in buffer capacity) and establish anelectrochemical potential that acts as a kind of battery or reservoir of stored energy for the cell. The inner cell membrane functions in a similar way to a dam in a river. It blocks protons from drifting back into the matrix. Since the pumping action is against the gradient, it requires work (energy). The process is directly analogous to bicycling uphill or charging a battery (storing uppotential energy ). It is important to remember that the proton pump does not create energy. Instead, the gradient stores energy for the appropriate time.Mobility
Some of the enzymes involved in the
electron transport chain , such asubiquinone , travel along the matrix, like freight boats, navigating up and down the river.Others such as
NADH -Qreductase , act like ferryboats and cross the matrix. Enzymes that can cross the matrix may have a secondary role as proton pumps because they can deliver protons to the inner membrane.Diversity
In humans
In
mitochondria , reducing equivalents provided by electron transfer orphotosynthesis power this translocation of protons. For example, the translocation of protons bycytochrome c oxidase is powered by reducing equivalents provided by reducedcytochrome c . In theplasma membrane proton ATPase and in the ATPase proton pumps of other cellular membranes, ATP itself powers this transport.The FoF1
ATP synthase of mitochondria, in contrast, usually conduct protons from high to low concentration across the membrane while drawing energy from this flow to synthesize ATP. To allow the passage of protons a proton channel temporarily opens in the inner membrane.Non-humans
In bacteria and other ATP-producing organelles than mitochondria, ATP-producing organelles, reducing equivalents provided by electron transfer or
photosynthesis power the translocation of protons.CF1 ATP
ligase ofchloroplast s correspond to the human FoF1 ATP synthase in plants.Bacteriorhodopsin is a photosyntheticpigment used byarchaea , most notablyhalobacteria .ee also
*
transmembrane ATPase
*active transport
*cytochrome
*mitochondrion
*chloroplast
*electron transfer chain
*proton pump inhibitor
*ATP synthase
*V-ATPase
*GORD
*Kidney
*proton ATPase External links
*
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